Louisiana State Police and other officials say a reported explosion touched off a fire at the Williams olefins petrochemical plant in the Ascension Parish town of Geismar Thursday morning. One fatality has been confirmed, and 73 people have been transported from the site with injuries.

Ascension Parish Sheriff Jeff Wiley told The Advocate that the initial threat from the explosion has dissipated. However, "there are no guarantees" he says. State police say HAZMAT crews are on the scene, and that the fire has been extinguished.

The Louisiana Department of Environmental Quality is testing the air downwind of explosion and federal Environmental Protection Agency officials are en route, according to WRKF radio.

Approximately 600 people were inside the plant at the time of the explosion and subsequent fire at the plant located approximately 20 miles southeast of Baton Rouge.

The Louisiana Department of Environmental Quality told the Times-Picayune 33 or 34 people have been evacuated by ambulance and helicopter from the plant thus far.

State police say there are several burn injuries, and victims are being transported to Baton Rouge General Hospital.

The hospital is the recognized top burn unit in the area.

Residents of the area have been advised by officials to "shelter in place" during the emergency. The Louisiana Bucket Brigade's Ann Rolfes is en route to the area to speak with plant neighbors, she announced on Twitter.

The plant is near the intersection of Louisiana Highways 30 and 3115.

The Williams Companies, owners of the plant, said the explosion occurred at 8:37 a.m. and the flow of chemicals to the blaze was cut off by 10 a.m., according to a statement on their website.

At the onset of the incident, Louisiana State Police, Ascension OEP and Iberville OEP were notified. Both Ascension and Iberville OEPs activated their emergency alert systems.

We are currently focused on the safety and well-being of our employees, contractors and the local community who are responding to the situation. Emergency shut-down valves have been closed. The unit is isolated.

Our emergency-response crews are thoroughly trained to respond to these types of incidents and are diligently performing their work with their first priority being the safety and well-being of people in and around the area.

First responders are on the scene and local routes to the plant have been closed by the local authorities.

We are in the process of accounting for all personnel. Injuries have been reported, the number and extent of those injuries is not known at this point.

The company's website says the plant puts out about 1.3 billion pounds of ethylene and 90 million pounds of polymer grade propylene a year. The chemicals are the building blocks for different types of plastics.

The company says the local team is also "responsible for the ethane transportation business consisting of approximately 200 miles of pipelines, as well as a refinery-grade propylene splitter."